1. Field of the Invention
This invention relates to the art of pipe coupling devices and more particularly concerns ar improved retaining device for maintaining a sealed joint betwe'en a cylindrical end of one pipe and a bell at the end of arother pipe or pipe fitting.
2. Description of the Prior Art
It has been conventional practice heretofore, when a cylindrical end of a first pipe has been inserted into a bell at the end of a second pipe or a fitting, to effect a joint by mounting an annular or ring flange on the first cylindrical pipe. This flange is secured in place on the first pipe by setscrews. The ring flange has circumferentially spaced holes which register with corresponding holes in an annular flange at the free end of the bell of the second pipe. Bolts can be inserted through the registering holes and secured by nuts. In another construction, the holes in the free end of the bell are threaded and the connecting bolts are screwed into the holes in the bell without the use of nuts. The bolt heads abut the ring flange on the first pipe. These prior joint constructions present a number of difficulties and disadvantages. If the bell of the second pipe is warped, the holes in the free end of the bell do not register precisely with the holes in the ring flange on the first pipe. This misalignment makes it difficult to insert the connecting bolts. If one or more holes are enlarged in either flange to insert the connecting bolts, points of weak support for the bolts are caused, which can lead to later failure of the pipe joint. Another disadvantage is the rigidity of the joint. Any severe lateral bending or torsional twisting of the joined pipes with respect to each other causes intense strain on the connecting bolts which often break and failure of the joint then ensues. Another cause of prior joint failure is slippage of the set screws holding the ring; flange on the first pipe. These setscrews must oppose axial strains to which the coupled pipes are subjected. Since the setscrews are often smaller and weaker than the connecting bolts, failure of the joint occurs due to slippage or breakage of the setscrews when severe axially stresses and strains are applied to coaxially connected pipes. A further disadvantage is the time consuming assembly procedure required to insert and tighten the many connecting bolts and nuts in a properly balanced way. A still further objection is the great expense incurred for the large bolts, washers, nuts and other hardware, to secure the pipe joint. Where large pipes are to be installed ranging in size up to forty-eight inches or more, the expense for hardware is quite considerable.